add total superfluid delegation sum invariant

[antstalepresh]

Closes: #XXX

Description

---

For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[ValarDragon]

LGTM to merge once the API comment is resolved

[ValarDragon]

A couple of options:

• Refresh delegation immediately after a slash. (Make a new hook called AfterValidatorSlashed）
• Slash in parity with existing SDK code (not preferrable, existing SDK code is the one thats wrong)
• Make the invariant have an exception if in the same epoch as a slash
• Check the rounding on slashing. (Slash in SDK rounds once per IA, in our code rounds once every underlying lockup)
  • The answer is still refresh immediately, or make make the invariant have an edge case for same epoch as slash

[ValarDragon]

Can you PR the hook addition to the SDK branch, then we can get this merged?

[antstalepresh]

Here's the PR for after slash hook
https://github.com/osmosis-labs/cosmos-sdk/pull/136/files

[ValarDragon]

Just needs to update the go.mod reference to be merged commit in the SDK branch, and we can get this merged.

[codecov-commenter]

Codecov Report

Merging #1018 (815b550) into v7.x (8ce7b0d) will increase coverage by 0.11%.
The diff coverage is 60.41%.

@@            Coverage Diff             @@
##             v7.x    #1018      +/-   ##
==========================================
+ Coverage   20.59%   20.70%   +0.11%     
==========================================
  Files         193      194       +1     
  Lines       25231    25279      +48     
==========================================
+ Hits         5197     5235      +38     
- Misses      19082    19088       +6     
- Partials      952      956       +4     

Impacted Files	Coverage Δ
x/claim/keeper/hooks.go	28.00% <ø> (ø)
x/superfluid/keeper/hooks.go	61.90% <33.33%> (-4.77%)	⬇️
x/superfluid/keeper/invariants.go	54.05% <54.05%> (ø)
x/superfluid/keeper/intermediary_account.go	88.15% <100.00%> (+1.39%)	⬆️
x/superfluid/keeper/stake.go	58.82% <0.00%> (+4.70%)	⬆️
x/superfluid/keeper/keeper.go	100.00% <0.00%> (+6.25%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8ce7b0d...815b550. Read the comment docs.

[antstalepresh]

Here's cherry picked version of this PR that is to main branch. And closing this.
#1081